there is two term in motor number o 2

[prdpks2000]

there is two term in motor number of start -stop permitted;
Hot Start & Cold Start
how they are defined in standard; what exactly there mean; let say its written 2 consecutive hot start after what time duration we can give again the consecutive hot start.
what is significant of following consultant requirement;
Starting duty:
a) 2 consecutive starts from cold condition against full load.
b) 4 starts per hour against full load under hot condition. One hot restart without any pause to be permitted
c) 6 starts per hour for trial run during commissioning and occasional abnormal operating conditions.

 

[FacEngrPE]

Previously discussed in thread237-65535
See also IEC Std. 60034-12 and NEMA Std. MG 1
The NEMA definition for Two consecutive starts is
Two starts in succession (coasting to rest between starts) with the motor initially at the ambient temperature, providing
a. Applied voltage and frequency in accordance with [NEMA Standard] 12.44.
b. During the accelerating period, the connected load torque is equal to or less than a torque that varies as the square of the speed and is equal to 100% of rated-load torque at rated speed.

Safe Starting of Motors: Check for Temperature Increase; EP Editorial Staff | May 1, 2015

The other definitions are logically similar.
Failure to observe this constraint will eventually result in motor damage, such as broken rotar bars, and short winding life,

 

[prdpks2000]

what my understanding for HOT and cold condition ;

let motor is class F (Maximum 210Degree C short time permissible temperature ) temperature rise is limited to class B(Maximum limiting temperature is 185Degree C for short time permissible temperature) over ambient 40Degre C(allowed temperature rise in class B is 80 Degree over an ambient of 40Degree C)

Hot Condition : Motor winding at operating temperature i.e. 40 + 80=120Degree C
Cold Condition : Motor winding at Ambient i.e. 40 Degree C

so if motor is taking rated current we have to term its as Hot condition and motor which is taking no load current can be treated as cold condition.(as this has indirect measurement of temperature )

motor stall time is proportional to Θ(permissible rise in temperature in stalled condition ) which is in above motor case
Θ= for Hot Condition(185-40-80)=65 Degree and for cold condition (185-40)=145•C
Motor stall time is inversely proportional to (Ist/Ir)^2

Now after what time gap we can give consecutive start again :The period after which this can be repeated will depend upon the heating curve and the thermal time constant of the motor, i.e. the time the motor will take to reach thermal equilibrium after repeated starts